1. Field of the Invention
The present invention relates to a surface curvature measuring apparatus for object profiles. Particularly, the present invention relates to the surface curvature measuring apparatus having a magnetically attractable curvature-measuring module for measuring the object profiles. More particularly, the present invention also relates to the magnetically attractable curvature measuring module in use for measuring undersurfaces of the object profiles.
2. Description of the Related Art
Conventionally, a surface curvature measuring apparatus, as shown in FIG. 1, is arranged on a platform 1 and includes a bar height adjustment 11, a movable bar 12, a rotary mechanism 13 and a curvature-measuring module 14 which are mounted on the platform 1. The bar height adjustment 11 has a screw connection with the movable bar 12 that can be moved upwardly or downwardly along a vertical direction, and further includes a controllable adjusting wheel 111 to turn a screw rod on which the movable bar 12 is moved and adjusted. The movable bar 12 includes an upper shaft 121 mounted thereto. Correspondingly, the rotary device 13 includes a lower shaft 131 mounted thereto. When assembled, the upper shaft 121 and the lower shaft 131 are substantially in perfect alignment with each other. Mounted between the upper shaft 121 and the lower shaft 131 is a sample object 9 such as a propeller or a vane-like member or the like for measuring curvatures. The curvature-measuring module 14 includes a slide track 141, a slide 142 and a measuring rod 143. Such a measuring technique of the curvature-measuring module 14 has been widely disclosed in many Taiwanese patents, TWN Patent Pub. Nos. 543522 and 312336 for example.
To measure the surface profile, a hub portion of the sample object 9 is clamped between the upper shaft 121 and the lower shaft 131 and rotated about a common axis of the upper shaft 121 and the lower shaft 131. In measuring operation, the slide 142 is movably mounted on the slide track 141 and can be moved upwardly or downwardly thereon in a vertical direction during rotation of the sample object 9. Meanwhile, a top end of the measuring rod 143 connects with the slide 142 while a bottom end of the measuring rod 143 is in contact with a top surface of the sample object 9. The combination of the slide 142 and the measuring rod 143 has an adequate weight to maintain the bottom end of the measuring rod 143 in perfect contact with the top surface of the sample object 9. When the sample object 9 is rotated, the bottom end of the measuring rod 143 can be synchronously moved upwardly or downwardly on the top surface of the object 9.
Vertical positions (i.e. heights) of the slide 142 can be varied by changes in those of the bottom end of the measuring rod 143 which is run along the top surface of the sample object 9. Hence, there is a constant relationship between the vertical positions of the slide 142 and the bottom end of the measuring rod 143. This means that surface curvatures of the top surface of the sample object 9 can be given by the vertical positions of the slide 142. In measuring, data of the vertical positions of the slide 142 are output to a computer device via a transmission line for plotting a profile of the top surface of the sample object 9. Such a top-surface profile of the sample object 9 can be used to analyze hydrodynamics.
Although it would be advantageous to measure the surface curvature of the top surface of the sample object 9, an undersurface thereof cannot be measured at the same time for same selected points of contours. Another problem with the single measurement of the undersurface subsequent to that of the top surface is the further need of turning the sample object 9 over and reassembling it on the apparatus. The primary problem with such a turning procedure may disadvantageously cause a need of realignment among the same selected points of the top surface and the undersurface of the sample object 9. Inevitably, there is a need of repeating the same steps of the previous measuring procedure for the undersurface of the sample object 9 that results in a low efficiency of the entire measurement.
In addition to the above, the bottom end of the measuring rod 143 is exactly in contact with the top surface of the sample object 9, and a downward force resulted from at least weights of the slide 142 and the measuring rod 143 is exerted on the sample object 9. A frictional force between the measuring rod 143 and the sample object 9 may cause a tilt of the measuring rod 143 to its vertical direction. Furthermore, vanes of the sample object 9 are susceptible to distortion due to its thinner thickness if it is made from a thinner material. These must result in errors in the measurement. Hence, there is a need for improving the conventional measuring apparatus and eliminating high-degree errors in the measurement of the surface curvature.
As will be described in greater detail below, the present invention intends to provide a surface curvature measuring apparatus for object profiles. To accomplish an efficient curvature-measuring procedure, the surface curvature measuring apparatus has a magnetically attractable curvature-measuring module for accurately measuring an undersurface of a sample object. To further accomplish a two-side curvature-measuring procedure, the surface curvature measuring apparatus has a gravity curvature-measuring module corresponding to the magnetically attractable curvature-measuring module in such a way as to mitigate and overcome the above problem.